Like James Bond, the Harry Potter movies just keep chugging along, immune to the outside cinematic world, ensconced in their universe of quidditch and muggles, inferi and death eaters. They have perfectly fitted their source material from day one: each arriving regularly with a thud on the doormat every year or so since 2001, achieving a near-institutional status that has eluded the Narnia adaptations.

There had been mutterings, however, over this sixth in the Potter series, pushed back from its original planned release date last Christmas. Monkeying with the schedule tends to alert the paying public that all is not well. The Half-Blood Prince is adapted from JK Rowling's penultimate novel, but so desperate are the producers not to compromise their revenue stream that the final book, the Deathly Hallows, will be divided into two parts.

Nevertheless, there's little here to suggest there has been any let-up in the Potter machine. The eponymous schoolboy – still in owlish spectacles as he hits 17 or so – is up against skeletal blond Draco Malfoy, on some kind of vile mission from evil genius Voldemort. Hogwarts' main asset against him is Professor Horace Slughorn (played by Jim Broadbent in that cod-Dickensian style that is practically compulsory for the Potter cast). Slughorn's brain contains key memories of Voldemort's schooldays and Harry must extract them.

There's lots of blushing, stammering and smooching. Will Harry lock lips with Ginny? Is Ron smart enough to see that Hermione ... well, it's not Skins. Hands are kept above the waist at all times.

Putatively winsome all this may be, but what it actually does is throw the series' biggest weakness into sharp relief: film-making can (and does) control pretty much everything – except how the cute juvenile leads grow up. Still, director David Yates knows how to play all the cards. Although a touch ungainly, his film is solidly constructed, with lots of fine effects. If, as Potter approaches his final confrontation with Voldemort, the wizardly battles begin to resemble Lord of the Rings, it's hardly a handicap; this is tried and tested cinematic language, and does all it needs.

Charles Gant: The hormonal Hogwarts hero has earned more at the British box office than the Transformers can wave a wand at. And with no challenger in the pipeline, the wizard is set to be this summer's undisputed blockbuster champ